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Dr.DivX probs
Not sure about your first two questions. And regarding Dr.DivX, its now a open source project in Beta stage. DivX has a DivX create bundle as a replacement though its not as flexible as Dr.DivX
use VCDGear to pad and correct error in media file b4 rendering it to dr.divx it might help & pass 2 error might not occur. u can't set any framework to decide best compromise between size and qualilty it depends more on original size of media file. and i recommend not to use any additional prog. while running dr.divx as it will increase cpu burden and sometime results in operation failure due to cpu bottleneck.